Dominion Greying out posts seems more appropriate to something like locked or deleted threads.
Perhaps ... but on the other hand, one could argue that usually a thread is only of interest to you if it contains new posts, and therefore that state should be associated with the "normal" font style. Everything else is less important and thus should be less prominent than "normal".
It's worth mentioning that this is also the approach that Discourse takes.
Anyway, I've switched over the styles on this forum so we can give it a go. Note that I haven't made a third bold state for followed posts – Dominion makes a good point that three states are less intuitive than two. Also note that if we went ahead with this change, we would want all titles to still be black for visitors who aren't logged in, not grey like they are now ... but that would involve some changes to the code, which is why I haven't bothered for now.
Thoughts?